To say mostly iron and carbon is pretty misleading. The most common grade of steel sheet contains 0.08% carbon. A high carbon spring steel would be 0.95% carbon. The most common grade of stainless steel contains 18% Chromium and 8% nickel and 0.08% maximum carbon. Almost all steel grades and alloys contain more manganese or other trace elements than carbon.

primarily iron & carbon w/trace amounts of elements (depending on composition desired) including or more of the following: manganese, nickel, chromium, boron, titanium, tungsten, cobalt, phosphorus, sulfur, silicon, and a few others most ppl have never/rarely heard of